Sky & Telescope - May 2024 - 29

& Telescope operates an aurora tour each
fall: https://is.gd/SnTiceland.
Aurorae are easier to see in the Northern
Hemisphere. This is because the
auroral oval extends over easily accessible
lands, whereas the southern oval is mostly
confined to Antarctica and the Southern
Ocean, though it occasionally extends to
points visible from southern New Zealand,
Tasmania, and southern Australia.
The " goldilocks zone, " so to speak, is
the auroral oval that manifests around
the geomagnetic North and South poles.
This is where energy funnels through the
magnetosphere on a near-constant basis.
That means locations under this oval see
the aurora almost every night. However,
this oval is usually above the Arctic Circle,
or 66° north, where the Sun never sets
during summer months. Aurorae are also
most frequently seen around the equinoxes
in late April and September.
Given that all of these places tend
to be very cold, be sure to dress warmly
when heading out on your vigil.
The auroral oval surrounds the geomagnetic
poles, which are significantly
offset almost 10° in latitude from the
rotational poles. In the north, the magnetic
pole is currently located within
the Arctic Archipelago in northernmost
Canada. This offset allows for some midlatitude
locations to be better choices than
others. Quite often, the southern shores of
the Great Lakes region in the United States
are treated to more auroral displays than
the more northerly locations of the Pacific
Northwest and New England. Overall,
planning to see the northern lights at midlatitudes
is challenging, to say the least.
But it's always good to have a location in
your back pocket in case you find yourself
on vacation in a northern-tiered spot during
an aurora event.
It's also useful to be aware of a phenomenon
called magnetic midnight. This is
when the north or south magnetic pole is
directly between the Sun and the observer.
Due to the offset of the geomagnetic poles,
the area of the strongest auroral activity
is always opposite of the Sun's position, so
the area of likely activity rises and sets as
seen from lower latitudes.
For example, in the Great Lakes region,
on a night with auroral activity, it will be
REQUISITE TOOLS While your smartphone
may be able to take a respectable image of a
bright aurora, you'll have much better results
using a digital camera that accepts interchangeable
lenses. Serious aurora photography requires
a high-quality wide-angle lens, a shutter-release
device, and a sturdy tripod.
WEATHER MONITOR The smartphone app
SpaceWeatherLive presents important real-time
information to help you determine if it's worth
heading out to shoot aurorae. The four graphs
presented here are the most important ones to
watch, as described in the article.
visible towards the northeast after sunset,
progress to the north, and then move
towards the northwest towards morning.
Because of the offset between the
geomagnetic and geographic poles, the
exact time changes slightly from location
to location. Magnetic midnight is helpful
knowledge when chasing during nights of
lower activity, so you know which direction
of the horizon to monitor for the
best chance of activity.
Visual Expectations and Photography
Witnessing
a good auroral display is often
mesmerizing but not as colorful as shown
in photographs. Particularly strong
storms may be bright enough to generate
greenish and reddish ribbons, rays, and
curtains but with hues more muted than
in photos. Typically, we perceive aurorae
in shades of grey with a dash of green
tint. That's if you are lucky and catch an
event that's bright enough to activate the
sk yand tele scope .o r g * MAY 2024 29
https://www.is.gd/SnTiceland http://skyandtelescoper.org
Sky & Telescope - May 2024

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